Shutters have become the universal decorative element.

You can find them on new "colonial" rowhouses and on almost every suburban ranch house in America. Drive down any street and you will see 12-inch wide shutters on every window of the house, including both sides of a four-foot wide picture window. They will more than likely be made of molded plastic and nailed to the siding. Few, if any, will serve their original purpose: to "shut up" a house, to protect it from break-ins.

Shutter has become the common name for two different things. Originally, shutters had solid panels and were attached to the outside of the house with hinges that allowed them to be closed from the inside. They were heavy enough to keep out intruders and thick enough to protect the panes of very expensive windows glass from the flying debris of a storm.

What are now often calles shutters, movable louvers set in frames and attached to the inside of the window were originally "blinds." These blinds were an inexpensive yet effective means of climate control.

In the winter, the blinds on the sunnyside of the house could be opened to warm the interior during the day and closed at night to reduce the amount of warm air escaping through the glass. In the summer, the window could be opened and the blinds closed. A breeze could move through the house but the sun's heat would be blocked out.

Blinds were painted to match the window frame. They often had one solid panel so that when they were folded against the frame, they appealed to be part of the woodwork.

If your old house has its original blinds or shutters, keep and repair them. If they have been lost or thrown away, the replacements should match the style of the house.

Do not put exterior shutters on a house that never had them. There might not be enough room for them on the facade and in trying to fit them to the space you could create the anomaly of one shutter between two windows.

Check the hinges of the shutters twice a year. Their weight and the action of opening and closing, can loosen the screws. If this has happened and tightening the screw does not work, remove the screw, fill the cavity with wood putty, and reset the screw.

Many blinds have missing louvers. These can and should be replaced. The louvers have pegs at both ends that fit into a socket in the frame. A replacement louver should be cut from quarter-inch thick pine, the size of the original. A finishing nail sharpened at both ends is a good substitute for a peg. Take one nail, bend it into a "U" and drive it part way into one end of the new louver.

Take a second nail, sharpened and bent the same way, and drive it almost completely into the other end. Slip the first end with the partially driven "nail" into its socket. Take the other end and place it over the other socket and with a screwdrive pull the nail out of the louver and ease the new peg into the socket.

Beverly Reece is associated with the Preservation Resource Group, which conducts building preservation workshops here.